The present invention relates to a dextrose in powder form with a high dextrose content and a substantially α crystalline form, having a particular water content and of which the industrial use properties, particularly in direct compression, are improved.
The present invention also relates to a dextrose hydrate in powder form having a remarkable density and particle size and also having good flowability, and to a process for the preparation thereof.
Within the meaning of the invention, the term “dextrose hydrate in powder form” means a dextrose in powder form having a water content greater than 1%, preferably in the range 2% to 10% and even more preferably from 5% to 9.5%.
Dextrose, produced industrially by hydrolysis of various starches, has been commonly used, mainly in the food industry, for numerous years.
It is used to advantage in applications where it is necessary to have products in powder form, for example, for the production of tablets, chocolates, Viennese bread and buns, cakes and pastries, nutrient compositions for plants or various mixtures in powder form where it usually acts as a sweetener, osmotic agent, nutrient and/or excipient.
Three crystalline forms of dextrose are conventionally described, i.e. α dextrose monohydrate, anhydrous α dextrose and anhydrous β dextrose.
Although numerous processes have been proposed for directly converting glucose solutions into solid materials of any crystalline form, α dextrose monohydrate remains the virtually exclusive source of dextrose powder.
This α dextrose monohydrate is conventionally produced by slow crystallisation, by cooling supersaturated syrups with a high glucose content originating from the hydrolysis of starch.
However, any dextrose in powder form composed of this sole crystalline species and prepared in the conventional manner is generally not very compressible, and it is necessary to add maltodextrins or polysaccharides to it for the production of tablets. In spite of this, the products prepared in this way have generally been unsatisfactory because of problems of agglomeration and handling due to the maltodextrins or polysaccharides.
Anhydrous α crystalline dextrose, a very pure crystalline dextrose with a low water content, i.e. at most equal to 1%, was therefore chosen.
This anhydrous α dextrose is generally produced by crystallisation of glucose at temperatures in the range 50° C. to 65° C., for example, by evapocrystallisation in autoclaves under high vacuum and under carefully controlled operating conditions.
However, the anhydrous α dextrose thus obtained has the disadvantages of dissolving relatively slowly in water and having a tendency to cake during dissolution. In fact, a part of the anhydrous α dextrose is converted once again during this dissolution to α dextrose monohydrate which agglomerates and delays the dissolution of the anhydrous α dextrose accordingly.
In order to dissolve satisfactorily the two α monohydrate and anhydrous α forms, it is necessary, therefore, to use water at high temperature or to add the dextrose gradually to water with stirring.
It was then proposed, therefore, to use an anhydrous β crystalline dextrose which has a much better rate of dissolution compared with that of anhydrous α dextrose and even monohydrate.
However, it is well known to experts in the crystallisation of dextrose that although the transition point of the crystallisation of α dextrose monohydrate to anhydrous α dextrose is about 55° C., that of anhydrous α dextrose to anhydrous β dextrose is about 110° C.
It follows that, in order to obtain anhydrous β dextrose, it is necessary to operate at a very high temperature at which dextrose is not very stable. This result limits all the more the industrial use of such a crystallisation process.
Patent application FR 2.398.802 describes a dextrose in powder form which has good flowability, does not agglomerate, is appreciably free from an unpleasant taste and coloured impurities but also has satisfactory compression properties. The authors of this patent point out, however, that this dextrose in powder form is, in fact, composed of a mixture, in roughly equivalent amounts, of anhydrous α and β dextrose. The process for the preparation thereof by crystallisation and granulation is, moreover, particularly long and tedious.
It is apparent from the above that there is an unsatisfied need to obtain a dextrose hydrate in powder form with a high glucose content and high crystalline purity and which also has excellent compressibility and very good flowability.